A data recording apparatus capable of selectively recording digital and analog audio signals is known. A product of Matsushita Electric Industry Corp. (Model Number SV-D1000) has been sold since 1987 as a digital audio tape recorder (hereinbelow also referred to as DAT). FIG. 10 is a block diagram of this DAT. In FIG. 10, numeral 11 indicates an A/D converter. Numeral 21 indicates a digital input decoder for decoding a digital input signal, from a terminal 20. The input is specified by a standard (IEC-958) specifying digital audio interfaces used to produce digital audio and sub-code signals. Numeral 22 indicates a digital copy control signal detection circuit for detecting a digital copy control signal included in the sub-code signal. Numeral 24 indicates a synchronizing error detection circuit for detecting errors in bit synchronizing or frame synchronizing. Numeral 30 indicates a record signal selector for selecting either an output signal of the A/D converter 11 or an output signal of the digital input decoder 21. Numeral 31 indicates a muting processing circuit for muting the record signal. Numeral 400 indicates a system controlling section for controlling operation of the system. The system controlling section 400 includes a microprocessor for controlling the whole system using communication through its input and output ports with peripheral circuits as well as inherent logical calculation processing capabilities. Since the structure of the microprocessor (mpu) is well-known, a detailed description is not necessary. FIG. 11 is a flow chart of the control operation of the prior art DAT shown in FIG. 10. A program stored in the system controlling section 400 is provided such that the system controlling section 400 operates in accordance with the flow chart of FIG. 11. Numeral 410 included in the system controlling section 400 indicates a permission/inhibition determination section for making a determination as to permission/inhibition of digital copying in accordance with the digital copy controlling and synchronizing error detection signals. Numeral 420 indicates a digital copying recording controlling signal generation section included in the system controlling section for generating a digital controlling signal to be recorded on a recording medium. Numeral 51 indicates a sub-code encoder for converting the digital copy controlling signal into a sub-code formatted signal. Numeral 50 indicates a record signal processing circuit for converting the audio digital and sub-code signals into a record format signal. Numeral 52 indicates a recording circuit. Numeral 53 indicates a head. Numeral 54 indicates a magnetic tape. Numeral 60 indicates a operation switch and numeral 70 is an indicator.
Operation of a conventional data recording apparatus having the above-mentioned structure is described with reference to FIG. 11, a flow chart of the operation control of the system controlling section 400. When a command for the digital copy mode is made by the operation switch 60 (step 202), an operation mode controlling section 430 included in the system controlling section 400 controls the record signal selector 30 to select the digital input signal at terminal 20. At the same time, the mpu detects synchronizing condition and determines permission/inhibition of digital copying. If the result of the determination indicates "permission", the mpu places the recording circuit 52 in recording state (step 205) with the digital copy control signal. If the result shows "inhibition", the mpu prevents the recording circuit 52 from being in the recording state and indicates that "digital copying is forbidden" by providing a flickering indication to show a user that some counter operation (step 206) is appropriate.
After the start of the recording operation (step 205) with selection of the digital input signal, the mpu detects synchronizing error and digital copy controlling signal (steps 207 and 209). If synchronizing is not in error and the digital copy controlling signal indicates permission for copying, the mpu maintains the digital copying operation (step 211). If synchronizing is in error and the digital copy controlling signal indicates inhibition of copying, the mpu controls the muting processing circuit 31 so that a muted signal is recorded step 212).
An error in synchronizing may occur because the receiving side cannot respond to a change in the sampling frequency when the sampling frequency of the digital signal is changed. For example, when a satellite broadcasting signal is received directly, a synchronizing error occurs when the mode is changed between the A mode and B mode. This is because the sampling frequencies of A and B modes are different from each other. Then, during the synchronizing error interval, the muted signal is recorded. Further, if the number of copies permitted is specified and recorded on a recording medium for copyright purposes, when this magnetic tape is reproduced, the digital copying controlling signal may change from permission to inhibition of digital copying. Thus, if copying is carried out from such a magnetic tape to another magnetic tape, some portion of the other magnetic tape would include muted portions so that the copied tape would be different from one that the operator intended to make. In other words, the recorded program would not be continuous.
According to the above-mentioned conventional system, the operator can carry out digital copying if the operator acknowledges that the input signal is one permitted for digital copying. However, if the operator does not know such information and tries to select the digital copy mode to record the input signal he does not know if digital copying will be successful. As stated, it is very inconvenient when the operator does not know whether digital copying is permitted or not when he is recording the digital audio input signal by the DAT because there are digital audio signals for which digital copying is both permitted and not permitted. The problem has been dealt with in the following manner.
If an analog signal is available from the same source and includes the same content as the digital audio signal, the analog signal is supplied to the analog signal input terminal 10 and then the apparatus is placed into analog recording mode in response to the operation switch 60. Then the content can be copies using the analog signal instead of the digital signal. Further, if a synchronizing error develops during digital copying or a control signal indicative of inhibition of digital copying is detected during digital copying, a muted signal is recorded and an alarm is activated. In response to this, the operator temporarily stops recording and then changes the apparatus into the analog recording mode with the operation switch 60, so that he can copy the analog signal having the same content as the digital audio signal. However, it is very inconvenient for the operator to monitor the recording condition continuously in order to change the signal being recorded and to change the operation mode of the apparatus as necessary. Further, even though the problem of attempting to record muted signals is removed, another problem arises, a portion of the content of the input signal is missing due to recording stoppage. In other words, the sound or the program recorded on the magnetic tape is discontinuous.